Slope calculation and coordinate system problem

Discussion created by lminer78 on Feb 7, 2011
Latest reply on Apr 20, 2012 by erice-esristaff
I've got several elevation rasters in Mapinfo's tabbed grid format. I need to get them into ArcGIS, create rasters of the slope, and then average these values up by zone so I have a value of average slope per zone. My problem is that when I do this, I get values that make no sense. I think I have some problem with projections/coordinate systems.

The process I've gone through is as follows:
1. Open the mapinfo elevation raster in Global Mapper and export to DEM format
2. Run the DEM to Raster tool in ArcGIS without modifying the Z-value
3. Run the Slope tool from the Spatial Analyst toolset in ArcGIS to create a raster of the slope
4. Run Zonal Statistics as Table from the Spatial Analyst toolset

In terms of coordinate systems:
1. The original rasters are in WGS_1984_UTM_Zone_48N as is my dataframe.
2. I had to hand digitize my zones and they're in GCS_WGS_1984. I've tried reprojecting them to WGS_1984_UTM_Zone_48N with no apparent effect.

Am I doing something wrong here?